The campaign, created by M&C Saatchi, promoted the shot-sized caffeinated drink, Lucozade Alert Plus, and aired on Channel 4 and its digital service 4oD.
Despite receiving 81 complaints from TV viewers who had found the ad misleading and irresponsible, "because it implied the product could improve your reaction times and help you avoid accidents", the ASA defended it.
The watchdog noted the ad did not depict the product solely as a tool to improve reaction speeds, and recalled advice from the Department for Transport that said a "caffeine drink was a useful short-term solution to driver tiredness".
GlaxoSmithKline, which makes Lucozade, pointed to evidence that showed a product containing 40mg of caffeine and 60mg of glucose could have a positive effect on mental performance.
The company said it did not consider the ad implied the product simply improved reaction speeds, but, through the animated sequence, showed how it boosted mental performance and alertness.
The driver in the ad visualised the different options and took a route that avoided hitting a deer.
GlaxoSmithKline pointed out that the ASA had not upheld complaints about the effect of its caffeine and glucose drinks on brain activity in the past, concluding evidence showed a product containing 40 mg of caffeine and 60 mg of glucose could have a positive effect on mental performance.